WOOD RESEARCH Volume 68, Number 1, 2023
Nduduzo Khumalo, Masulubanye S. Mohomane, Linda Z. Linganiso, Cebisa E. Linganiso, Sandile Songca, and Motaung E. Tshwafo

Effect of acid hydrolyses on properties of cellulose/poly furfural alcohol (PFA) composites from maize stalk

The study investigated morphology and thermal properties of cellulose/poly furfural alcohol (PFA) composites prepared from maize stalk through acid mixtures. The cellulose nanocrystals (CNCs) were extracted from maize stalk via acid hydrolysis using mixtures of various acids. The prepared CNCs were encapsulated in a PFA matrix via in situ polymerization process using p-toluene sulfonic acid as catalyst. The properties of untreated maize stalk, cellulose and their nanocomposites were analysed by scanning electron microscope (SEM), X-ray diffraction (XRD), Fourier transmission infrared (FTIR) and thermogravimetric analysis (TGA). The crystallinity of maize stalk was generally increased after an acid hydrolysis dominated by H2SO4/HNO3 and H2SO4/HCl. The same trend was observed from TGA, except that H2SO4/H3PO4 and H2SO4/HClO4 dominated thermal stability trailed by H2SO4 hydrolysed CNC nanocomposite. The surface breakage of fibers observed in SEM images was depended on the strength of acids used to hydrolysed the CNC. There was also evidence of aggregation and cracked PFA surface with addition of acid hydrolysed CNCs, dependent on the acids strength. The H2SO4/HClO4 hydrolysed CNC/PFA displayed a fairly good dispersion of CNCs in the PFA matrix with no surface breakage.

WOOD RESEARCH Volume 67, Number 6, 2022
Nduduzo Khumalo, Samson Mohomane, Setumo V. Motloung, Lehlohonolo Koao, Malevu D. Thembinkosi, and Tshwafo E. Motaung

Effect of H2SO4/HCLO4 mixture on properties of sugarcane bagasse cellulose crystals

The main objective of the study was to investigate the effect of mixed acid concentration on the morphology, crystallinity and thermal properties of cellulose nanocrystals (CNCs). Acid hydrolysis using mixture of sulphuric (H2SO4) acid and perchloric (HClO4) acid was used to extract CNCs from sugarcane bagasse (SCB). The properties of the raw SCB, extracted cellulose, 45% H2SO4 hydrolysed CNCs, 45% H2SO4/HClO4 hydrolysed CNCs, 55% H2SO4/HClO4 hydrolysed CNCs and 65% H2SO4/HClO4 hydrolysed CNCs were analysed using Fourier transmission infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The crystallinity of SCB was significantly increased after bleaching and acid hydrolysis. Acid hydrolysis using 55% H2SO4/HClO4 showed the highest crystallinity. The TGA results showed significant increase in thermal stability of 55% H2SO4/HClO4. The lowest thermal stability was observed with 45% H2SO4 hydrolysed CNCs. The order of thermal stability was raw SCB < extracted cellulose < 45% H2SO4 hydrolysed CNCs < 65% H2SO4/HClO4 hydrolysed CNCs < 45% H2SO4/HClO4 hydrolysed CNCs < 55% H2SO4/HClO4 hydrolysed CNCs. The SEM results showed fibre breakage for 65% H2SO4/HClO4 hydrolysed CNCs. The fibre breakage seemed to be acid concentration dependent.

WOOD RESEARCH Volume 62, Number 6, 2017
Samson M. Mohomane, Linda Z. Linganiso, Thuli Buthelezi, and Tshwafo E. Motaung

Effect of extraction period on properties of sugarcane bagasse and softwood chips cellulose

This work evaluates the extraction of sugarcane bagasse (SCB) and soft wood (SW) celluloses with alkali treatment followed by bleaching process using sodium chlorite at different time. The influence of extraction time (2 hrs and 4 hrs) on the thermal, crystallinity and morphological properties was investigated. The extracted celluloses were analysed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transmission infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The aromatic skeletal vibrations of lignin and hemicellulose confirmed the extraction of cellulose which varied extraction time. TGA analysis shows that the untreated SCB degrade earlier than their respective celluloses and the prolonged treatment affects the onset of main degradation. XRD results showed that extracted celluloses had greater crystallinity index, and was affected at prolonged time due to long range destruction of cellulose crystals. The SW revealed a complex behaviour due to the dominated lignin content as revealed from chemical composition analyses.

WOOD RESEARCH Volume 62, Number 3, 2017
Martin Zachar, Andrea Majlingová, Iveta Mitterová, and IVETA ČABALOVÁ

Influence of an age and damage of the oak wood on its fire risk

The aim of this work is to study the effects of different ages and damage of the oak wood (Quercus petraea Mattusch) in relation to its flash point temperature and ignition temperature, as well as on determination of the ratio of changes in extractives, cellulose and lignin, in the heat loaded samples of 5 – years old oak wood, 160 – years old oak wood, and also 160 – years old oak wood degraded by wood-destroying insects and fungi. The results of the analyses showed that the flash point temperatures were in the range of 357.52°C – 360.63°C.The ignition temperatures were at interval of 398.93°C – 414.92°C. The time to reach the ignition point was at the interval between 344 and 365 seconds. Under the thermal loading of oak wood, there comes to the significant changes, especially in the surface layers. These are, in addition to colour changes, demonstrated the chemical changes of the main components of wood and extractives. Increasing the temperature, there increases also the content of the substances extractable with ethanol and toluene. Increase in their amount is mainly due to the lignin, but partially also due to the polysaccharides decomposition products.

WOOD RESEARCH Volume 63, Number 5, 2018
N.N. Sibiya, M.J. Mochane, T.E. Motaung, L.Z. Linganiso, and S.P. Hlangothi

Morphology and properties of sugarcane bagasse cellulose- natural rubber composites

This study investigated the mechanically treated sugarcane bagasse cellulose / natural rubber composites. The novelty of this work is based on sugarcane bagasse treated by supermass colloider and an acidification. Properties such as morphology, solvent uptake, diffusion coefficient, transport mechanism, and thermal stability of vulcanised natural rubber (RB) and its composites were investigated. The acid and mechanical treatment showed less aggregates in the composites than bagasse cellulose composite. The transportation mechanism of solvent diffusion suggested that irregular particles are responsible for solvent absorptions. The composites generally showed reduction in swelling rate which was attributed to tortuosity of the path and reduced transport area in the composites compared to neat natural rubber. There was a decrease in the thermal properties of natural rubber with the addition of the reinforcing fillers.

WOOD RESEARCH Volume 63, Number 5, 2018
Vladimir Ilyich Fedyukov, Mikhail Vladimirovich Boyarsky, Ekaterina Yuryevna Saldaeva, Maria Sergeyevna Chernova, and Vasiliy Yuryevich Chernov

Dependence of spruce wood resonance properties on its chemical composition

Nowadays there are no reasoned scientific data on inter relation of resonant properties of spruce-tree wood and its chemical composition. Thus the purpose of the study was to reveal the features of sonorous spruce in view of the content of basic organic substances in their timber. 20 model trees at the age of 180-190 years were selected as material for studies in taiga woods in the north of Kirov region of Russia. Special 0.5 m long blocks were made from each model tree at height of 1.3 m. Standard 20×20×300 mm samples were made from those blocks. Test samples were kept at room dry conditions for 2 years. After that dendro acoustic studies were carried out on them to define acoustic constant in different directions with respect to timber fibers. Further the percentage of cellulose, lignin, extractives and ashes in them was defined applying standard techniques. As a whole the chemical composition of spruce tree resonant wood lies approximately within the same limits as in common wood of the breed given. However significant influence of cellulose on a longitudinal acoustic constant and lignin on a radial constant is revealed. Joint influence of lignin and cellulose on a tangential constant is found out, the influence of lignin in the latter case being dominant. Continuation of fundamental research in this field has great cognitive value for revealing the nature of unique acoustic properties formation in sonorous spruce wood. Such studies acquire special topicality when dealing with outstanding violins as well as the wood kept for many decades in old buildings subject to demolition.

WOOD RESEARCH Volume 63, Number 4, 2018
Chenah May and Amrani Moussa

Chemical and structural analysis of lignocellulosic biomass of Ampelodesmos mauritanicus (diss) and Stipa tenacissima

Chemical composition, anatomical characteristics and cell wall structure of Ampelodesmos mauritanicus (Diss) and Stipa tenacissima (Esparto grass) fibers were analyzed. The results reveal the % (W/W) holocellulose content of Diss and Esparto grass was found to be 54.39 % and 51.8 %, respectively. Esparto grass had the greatest % (W/W) lignin content of 32.2 % while Diss had the last lignin content of 24.95 %. Estimation of %( W/W) extractives contents in Diss and Esparto-grass were observed to be 12.03 % and 13.5 % in that order. According to XRD data, Diss showed, as expected, a lower crystallinity index (CI) 52.5 % when compared to Esparto grass samples 55.2 %. The results of the thermal decomposition of natural fibers are shifted to higher temperatures with increasing the cellulose crystallinity. Based on the results of the chemical composition of Diss and Esparto grass, it was confirmed that straw is rich in cellulosic fibers and, therefore, a valuable raw material for the paper and manufacture industry.

WOOD RESEARCH Volume 66, Number 4, 2021
Sahin Akyurek, Murat Akman, and Murat Ozalp

Effects of heat treatment on some chemical compound and mechanical properties of black pine wood

In this study, effects of heat treatment on bending strength, compression strength, chemical compound and solubility of Black pine wood (Pinus nigra J.F. var. seneriana) was examined. For this purpose, Black pine wood samples were kept in temperature of 250°C for 2 hours. Test results of heat-treated Black pine wood and control samples indicated that mechanical characteristics including compression strength and bending strength were affected negatively with heat treatment. Bending strength of heat treated and non-treated test samples were 129 and 76 N.mm-2, respectively. Compression strength of heat treated and non-treated test samples were 53 and 43 N.mm-2, resp. In addition, level of extractives, cellulose and hemicellulose decreased while lignin content increased with percentage of 40%. Significant decreases occurred in all chemical solubility values.

WOOD RESEARCH Volume 66, Number 1, 2021
Samson Masulubanye Mohomane, Setumo Victor Motloung, Lehlohonolo Fortune Koao, and Tshwafo Elias Motaung

Effect of silica on alkaline bagasse cellulose and softwood cellulose

This study investigates the effect of silica on sugarcane bagasse (SCB) and softwood (SW) cellulose. Cellulose was extracted from raw SCB and SW chips using a three-step process, namely thermal pre-treatment, alkaline treatment and bleaching treatment. Alkali treated cellulose was then subjected to silica surface modification using the solvent exchange method. The effect of silica modification on SCB and SW cellulos was investigated using X-ray diffractions analysis (XRD), Fourier transform infrared (FTIR) spectroscopy and optical microscope (OPM) techniques. Both the FTIR and XRD results confirm successful extraction of cellulose from both raw fibers and addition of silane functional groups in the cellulose surface. XRD patterns of all samples revealed typical spectra for natural fibers corresponding to crystalline peaks of cellulose and undissolved amorphous hemicellulose respectively. SCB and SW showed similar increasing patterns of crystallinity with nanosilica surface modification. The surface morphology results showed that both SCB and SW cellulose modified with silica were swollen and displayed small particles agglomerating on the surface of the fibers. The solvent exchange method proved to be a successful method for modifying SCB and SW cellulose with nanosilica. It also proved to be cost-efficient and time-efficient.